Can't connect to Cisco 877 router

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Hi

Someone dumped Cisco 877 router on my desk few days ago and I've been trying to get it to work since. I've got the original console cable but I don't know how the router is configured.

I've been trying to connect using Putty on 9600/8/1, 9600/8/2, 38400/8/1, 115200/8/1 but I wasn't able to connect (no output at all - just a blank putty window).

I tried holding the reset button pressed for couple of seconds during boot (30 secs) but it doesn't seem to make any difference.

The 'OK' light is lit up on the router.

Any ideas how to connect to it?

Cheers

 

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I think the reset button probably needs pressed when it is finished booting

Have you tried connecting to the switch ports and seeing if you pick up an IP.....mind you not much use if you don't know the password, but would prove it is workign if it does give an IP.

 

The default settings in Putty are fine, I use it as the default too for serial connections.

It should work if all connections are fine... Try turning it on with Putty already open? You should then see the boot process, during which you can access pwd recovery

 

Thanks. I'll take the router home for the weekend and try to find the IP address but as you say without a password it might not be very useful.

 

Thanks. That's what I have been doing. I get nothing in the putty window though. No boot process at all. Screen just stays blank.

 

Are you using the correct COM port (in the Putty options) by the way?

 

Yeah I've got only one COM port in device manager (COM1). Putty throws an error if I try to use anything else (COM2, 3 or 4)

 

Can you test your pc/laptop/com port/cable with another (known working) device?

These are all the valid console port speeds, i'd try them all with 8/1/N

1200
2400
4800
19200
38400
57600
115200

 

Thanks. Turns out the console cable was faulty.

 

After two wasted days, I finally managed to un-brick my Cisco 877. As we unlucky few have found, the symptom--namely that there is no console output during boot, and apparently no way to access the ROMMON prompt--is often met with well-intentioned suggestions... involving the ROMMON prompt. "It must be your 'BREAK' sequence" is the only advice on offer.

While it does seem odd that a 2000s era Cisco device might be bizarrely finicky about obscure electrical details of the EIA RS-232-C (1969) spec, anecdotal evidence for this has been lurking about during the 20+ years I've owned Cisco equipment. Witness, for example, the lengthy official Cisco treatise dedicated to the subject of serial BREAK, which includes 'helpful' details on the required signal voltages, minimum timings, and a tabular list of (mostly deprecated) 3rd party software. Or the dire insistence that a certain particular cable must be used (I have four of them, each tagged with some insistent variant of "CISCO!! ...this is the one that really works!")

Well it does so happen that electrical signals are at issue, but--at least for my case here--it had nothing to do with the BREAK sequence (a special manipulation of the data line), but rather, perhaps, the RS-232 control signals DTR and CTS (note that I'm not talking about flow control--whether hardware, in-band, etc.--and I believe the advice to disable those still stands). Assuming you have the right cable, the problem seems to relate to the detection, or "opening", of the serial port. If I recall the 1970s, the aforementioned signals (or ilk) may pertain to the presence (or absence) of a party on the other end of the serial link. I surmise that the 877 ROMMON only starts up console communication when its detects that its UART state has changed to "open."

Anyway, as I can repeatably demonstrate with 'Realterm', you have to wait until just after you turn on the router before opening the COM: port. In my testing, the router does not emit any output nor accept any input (and this includes BREAK) via a RS-232 console session if that connection was electrically pending, or "open" prior to router power-on. If I switch on the router first, and only then open the port on the client terminal, the router is revived: I get the boot log, and ROMMON is accessible.

I took the trouble to write this up because I know it's a long-standing frustration out there, and I never saw this solution in scouring everywhere. If this works for others, then my hope would be that not too much seemingly bricked Cisco routers have been discarded over the years, for lack of this info.